1 /* crypto/dh/dh_check.c */

     2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

     3  * All rights reserved.

     4  *

     5  * This package is an SSL implementation written

     6  * by Eric Young (eay@cryptsoft.com).

     7  * The implementation was written so as to conform with Netscapes SSL.

     8  * 

     9  * This library is free for commercial and non-commercial use as long as

    10  * the following conditions are aheared to.  The following conditions

    11  * apply to all code found in this distribution, be it the RC4, RSA,

    12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

    13  * included with this distribution is covered by the same copyright terms

    14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).

    15  * 

    16  * Copyright remains Eric Young's, and as such any Copyright notices in

    17  * the code are not to be removed.

    18  * If this package is used in a product, Eric Young should be given attribution

    19  * as the author of the parts of the library used.

    20  * This can be in the form of a textual message at program startup or

    21  * in documentation (online or textual) provided with the package.

    22  * 

    23  * Redistribution and use in source and binary forms, with or without

    24  * modification, are permitted provided that the following conditions

    25  * are met:

    26  * 1. Redistributions of source code must retain the copyright

    27  *    notice, this list of conditions and the following disclaimer.

    28  * 2. Redistributions in binary form must reproduce the above copyright

    29  *    notice, this list of conditions and the following disclaimer in the

    30  *    documentation and/or other materials provided with the distribution.

    31  * 3. All advertising materials mentioning features or use of this software

    32  *    must display the following acknowledgement:

    33  *    "This product includes cryptographic software written by

    34  *     Eric Young (eay@cryptsoft.com)"

    35  *    The word 'cryptographic' can be left out if the rouines from the library

    36  *    being used are not cryptographic related :-).

    37  * 4. If you include any Windows specific code (or a derivative thereof) from 

    38  *    the apps directory (application code) you must include an acknowledgement:

    39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

    40  * 

    41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

    42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

    45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

    46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

    47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

    48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

    49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

    50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

    51  * SUCH DAMAGE.

    52  * 

    53  * The licence and distribution terms for any publically available version or

    54  * derivative of this code cannot be changed.  i.e. this code cannot simply be

    55  * copied and put under another distribution licence

    56  * [including the GNU Public Licence.]

    57  */

    58 

    59 #include <stdio.h>

    60 #include "cryptlib.h"

    61 #include <openssl/bn.h>

    62 #include <openssl/dh.h>

    63 

    64 /* Check that p is a safe prime and

    65  * if g is 2, 3 or 5, check that it is a suitable generator

    66  * where

    67  * for 2, p mod 24 == 11

    68  * for 3, p mod 12 == 5

    69  * for 5, p mod 10 == 3 or 7

    70  * should hold.

    71  */

    72 

    73 EXPORT_C int DH_check(const DH *dh, int *ret)

    74 	{

    75 	int ok=0;

    76 	BN_CTX *ctx=NULL;

    77 	BN_ULONG l;

    78 	BIGNUM *q=NULL;

    79 

    80 	*ret=0;

    81 	ctx=BN_CTX_new();

    82 	if (ctx == NULL) goto err;

    83 	q=BN_new();

    84 	if (q == NULL) goto err;

    85 

    86 	if (BN_is_word(dh->g,DH_GENERATOR_2))

    87 		{

    88 		l=BN_mod_word(dh->p,24);

    89 		if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;

    90 		}

    91 #if 0

    92 	else if (BN_is_word(dh->g,DH_GENERATOR_3))

    93 		{

    94 		l=BN_mod_word(dh->p,12);

    95 		if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR;

    96 		}

    97 #endif

    98 	else if (BN_is_word(dh->g,DH_GENERATOR_5))

    99 		{

   100 		l=BN_mod_word(dh->p,10);

   101 		if ((l != 3) && (l != 7))

   102 			*ret|=DH_NOT_SUITABLE_GENERATOR;

   103 		}

   104 	else

   105 		*ret|=DH_UNABLE_TO_CHECK_GENERATOR;

   106 

   107 	if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL))

   108 		*ret|=DH_CHECK_P_NOT_PRIME;

   109 	else

   110 		{

   111 		if (!BN_rshift1(q,dh->p)) goto err;

   112 		if (!BN_is_prime_ex(q,BN_prime_checks,ctx,NULL))

   113 			*ret|=DH_CHECK_P_NOT_SAFE_PRIME;

   114 		}

   115 	ok=1;

   116 err:

   117 	if (ctx != NULL) BN_CTX_free(ctx);

   118 	if (q != NULL) BN_free(q);

   119 	return(ok);

   120 	}

   121 

   122 EXPORT_C int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)

   123 	{

   124 	int ok=0;

   125 	BIGNUM *q=NULL;

   126 

   127 	*ret=0;

   128 	q=BN_new();

   129 	if (q == NULL) goto err;

   130 	BN_set_word(q,1);

   131 	if (BN_cmp(pub_key,q) <= 0)

   132 		*ret|=DH_CHECK_PUBKEY_TOO_SMALL;

   133 	BN_copy(q,dh->p);

   134 	BN_sub_word(q,1);

   135 	if (BN_cmp(pub_key,q) >= 0)

   136 		*ret|=DH_CHECK_PUBKEY_TOO_LARGE;

   137 

   138 	ok = 1;

   139 err:

   140 	if (q != NULL) BN_free(q);

   141 	return(ok);

   142 	}